As conventionally used bone regeneration materials, calcium phosphates such as hydroxyapatite (HA) are known (see, for example, JP2010-273847, JP2003-260124, JP2009-132601, and JP2005-279078).
Recently, octacalcium phosphate (hereinafter, referred to as “OCP”) which is a precursor of HA has been proved to have higher action of promoting bone regeneration and higher bioabsorbability than other calcium phosphates such as HA and β-tricalcium phosphate (β-TCP) do (see, for example, JP2006-167445). Thus, OCP has especially excellent characteristics as a bone regeneration material among other calcium phosphates.
However, OCP is poor in shape-imparting property because it is an inorganic substance. Therefore, it is difficult to apply OCP by itself to regenerate an extensive bone defective part or the like. In light of this difficulty, use of a composite of OCP and collagen as a bone regeneration material has been proposed (see, for example, JP2006-167445).